V3 clauses in Standard German
There is some consensus in the literature about the acceptability of verb-third (V3) structures in Standard German: it is acceptable in biscuit conditionals (see Davison 1983 and much subsequent literature), but generally not acceptable elsewhere. Consider the biscuit conditional in (1).
(1) Wenn du Hunger hast, ich habe Kekse.
if you hunger have I have cookies
If you are hungry, I have cookies.
Assuming that the clause "wenn du Hunger hast" forms a constituent, a total of two constituents precede the finite verb in the matrix clause. We observe that (1) has a slightly different interpretation from most other conditionals: the speaker is understood to believe that she has cookies independently of whether the addressee is hungry.
Compare this to the hypothetical conditional in (2).
(2) Wenn Peter eingekauft hat, habe ich Kekse.
If Peter shopping has have I cookies
If Peter went shopping, I have cookies.
(2) is a standard hypothetical conditional: the speaker is taken to be unsure about whether or not she has cookies in the actual world - what she commits to is that in those worlds where Peter went shopping, she has cookies. We observe that switching the order of "ich" and "habe" in (2) leads to a fairly odd sentence - to the extent that it is acceptable, it is more likely to be interpreted along the lines of (1).
Many analyses of biscuit conditionals depend on this fact. What they ignore is that (1) is part of a larger pattern: conditional antecedents are not the only type of clause that can appear in a V3 construction, and in fact there is a systematic effect of the word order on the interpretation.
(3) Wenn/weil/bevor du lange suchst, der Schlüssel ist im Auto.
if/because/before you long search the key is in.the car
If/because/before you spend a lot of time searching, the key is in the car.
We observe that the sentences in (3) differ in meaning from the corresponding sentences with V2 word order.
(4) Wenn/weil/bevor du lange suchst, ist der Schlüssel im Auto.
To the extent that the sentences in (4) are interpretable, they express a (conditional/causal/temporal) relation between two propositions. The sentences in (3), on the other hand, seem to express a relation between a proposition and a speech act.
I propose to follow Krifka's (2015, 2017) analysis for biscuit conditionals and extend it to other types of complex V3 clauses: the V3 word oder causes the subordinate clauses in (3) to act as speech act modifiers: they attach above the CP layer of the matrix clause.